1. Set your intention.
Before meeting with your parents, know what your goal is and what you're coming for. Decide on your intention and what you want to accomplish with this conversation. This is not a time to vent and scream at your parents or confront them in an unhealthy way.
2. Define the rules for your parents.
Before you begin, tell your parents what you want from them—what are the rules of this conversation? Explain to them that this is not about blame, but rather you wanting them to understand you. You can say things like, "I'm just asking you to really listen to how I'm feeling about this. I just want you to understand so I know you can feel for me in all of this. Please don't feel you have to defend yourself. I'm talking to you because I care so much about our relationship that I want to work on it getting better."
3. Don't attack.
Focus on your feelings to help them understand how you felt as a child. You want to say things like, "I was really lonely and scared that summer when you went away and I couldn't reach you." That's much more effective than, "How in the world could you leave me that summer?"
4. Be specific.
Without blaming, give specific examples of when your parents hurt you—many times, parents don't even know you heard or saw something. Talk about what did they did. How did that make you feel? How has that affected you? What do you need today? If it's easier, put it in writing, and read it to your parents. It will take the pressure off having to remember everything.
5. Resolve for the future.
Figure out how you, as a family, can continue the dialogue you've started and try to put an end to any ongoing negative behavior, such as bad-mouthing or being used as a messenger between your parents. Talk to your parents about trying to end those behaviors and encourage them to be protective of you, their child, even as an adult. Going forward, focus on the love you have for each other and do things that are pleasant and bring out that love.